The emergence of a wide range of biologically active compounds of massive complexity has severely tested the ability of conventional synthetic chemistry to provide quantities of both natural and unnatural compounds for pharmacological evaluation. Enzymes have long been recognized as catalysts for stereoselective transformations in organic synthesis. We propose to develop the use of pyruvate aldolases as catalysts for stereospecific carbon-carbon bond formation. These enzymes catalyze the stereospecific condensation of pyruvate with an electrophile aldehyde to generate 2-keto-4-hydroxy carboxylic acids. This conserved four-carbon segment is ideally suited for further synthetic elaboration in the preparation of a wide range of biologically active compounds. We will first examine the substrate specificity of several pyruvate aldolases to examine their potential utility in synthesis. The 2-keto-4- hydroxy carboxylate framework will be modified using a combination of chemical and enzymatic methodologies, including decarboxylation, reductive amination and stereospecific reduction. Pyruvate aldolases will be utilized for the construction of 2-deoxy aldose sugars, alpha- amino acids, alpha-hydroxy acids, nitrogen and oxygen heterocycles, and carbocycles. The long-term goal of this work is to develop straightforward, practical routes to classes of compounds, such that derivatives which vary in substitution pattern or stereochemical configuration can be synthesized using the same methodology, by varying the choice of enzymes or reagents.